Apparatus for rotational molding of laminated hollow structures

ABSTRACT

Apparatus for rotational molding of laminated hollow structures from plastic material is disclosed. A first plastic material is rotationally molded to the inside surface of a hollow mold until the first plastic material is in a fused condition. A second plastic material is then released from a thermally insulated container, which may be positioned within the mold and rotated with the mold, by air pressure moving an air piston attached to a cover of the insulated container to separate the cover from the insulated container. A bond is formed between the first and second plastic materials while the second plastic material is rotationally molded to the inside surface of the first plastic material to thus laminate the two materials together. After both materials are molded, the mold is cooled, rotation of the mold is stopped, and the molded structure is removed from the mold.

Patent For-mo APPA 11 ATUS FOR ROTATIONAL MOLDHNG OF LAMINATED HOLLOWSTRUCTURES lnventor: Jerome L. Formo, Saint Paul, Minn.

Assignee: Plastics, Inc., Saint Paul, Minn.

Filed: Dec. 17, 1969 Appl. No.: 885,911

References Cited UNITED STATES PATENTS 9/1967 Barnett et al. ..264/311 X2/1966 Lorentz et al... ..156/582 X 3/1967 Nonweiler ..264/3ll X [4 1Mar. 28, 1972 Primary Examiner-Samuel W. Engle Assistant Examiner-G. E.Montone Attorney-Wicks and Nemer [57] ABSTRACT Apparatus for rotationalmolding of laminated hollow structures from plastic material isdisclosed. A first plastic material is rotationally molded to the insidesurface of a hollow mold until the first plastic material is in a fusedcondition. A second plastic material is then released from a thermallyinsulated container, which may be positioned within the mold and rotatedwith the mold, by air pressure moving an air piston attached to a coverof the insulated container to separate the cover from the insulatedcontainer. A bond is formed between the first and second plasticmaterials while the second plastic material is rotationally molded tothe'inside surface of the first plastic material to thus laminate thetwo materials together. After both materials are molded, the mold iscooled, rotation of the mold is stopped, and the molded structure isremoved from the mold.

4 Claims, 5 Drawing Figures PATENTED MR 2 8 I972 SHEET 2 OF 2 I'NVENTOR.JEROME 1., FOR/4O FIEZE BACKGROUND The present invention deals withhollow, rotationally molded, plastic structures, more particularly witha novel method and apparatus for making such structures, andspecifically with a novel method, and apparatus performing according tothat method, for rotationally molding laminated hollow structures fromat least two plastic materials.

Plastic has proven a useful material for containers of liquid, forexample gasoline tanks, and rotational molding has been found to be aneffective method of manufacturing such containers. If a gasoline tank isrotationally molded from a relatively inexpensive plastic such aspolyethylene and the tank is clamped in position, the combination of thepressure and chemical action of the gasoline on the polyethylene maycause stress cracking of the tank. A nylon tank may be used since theaction of gasoline on nylon does not result in stress cracking, butnylon is relatively expensive. An entire tank of nylon is not necessaryand in addition is not practical from a cost standpoint. A lessexpensive but entirely suitable tank would have an inside surface ofnylon to avoid stress cracking and chemical reactions and an outsidesurface of polyethylene for support.

In the past, however, difficulties have been encountered in bonding twoplastic materials together in a rotational mold such as to form aninside surface of one material and an outside surface of the othermaterial. The present invention provides a method of so bonding twoplastic materials and apparatus performing according to that method.

SUMMARY Briefly, a preferred embodiment of apparatus operating accordingto the method of the present invention includes rotational moldingapparatus for simultaneously rotating a heated hollow mold upon twoaxes. The mold itself consists of two halves which are joined formolding and may be separated to remove the molded structure. A firstplastic material is added to the interior of the mold, the mold isjoined, rotated, and heated, and the first material is molded to theinside of the hollow mold.

An insulated container is supported within the hollow mold so as tonegligibly affect the molding process and so as to hold a second plasticmaterial in a thermally insulated state from the first material. Thesecond plastic material is preferably added to the insulated containerat the same time the first plastic material is added to the interior ofthe mold, before the mold halves are joined. The insulated containerincludes a cover which may be separated from the insulated container bythe application of fluid pressure upon the face of a piston attached tothe cover of the insulated container. Upon the application of fluidpressure, the cover separates from the insulated container and thesecond plastic material is allowed to enter the interior of the hollowmold.

As the second plastic material comes into contact with the first plasticmaterial maintained in a fused state, heat from the first plasticmaterial and the interior of the mold brings the second plastic materialto the fusion state also. The second plastic material is molded to theinside surface of the first plastic material by additional rotation andby mold heating. The mold is then cooled, and a bond is formed betweenthe first and second plastic materials by virtue of the first and secondplastic materials cooling through their melting points together. Thebond between the first and second plastic materials produces an integralhollow laminated plastic structure according to the mold configuration.When the mold has properly cooled, the halves of the mold are separated,and the molded structure removed.

It is therefore an object of the present invention to provide a methodand apparatus performing according to that method for rotationallymolding hollow laminated plastic structures.

This and further objects and advantages of the present invention willbecome clearer in the light of the following detailed description of anillustrative embodiment of this invention described in connection withthe drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 shows a top plan view of moldingapparatus capable of simultaneous rotational movement about two axesseparated from one another which molding apparatus operates according tothe method of the present invention.

FIG. 2 is a side view of the molding apparatus of FIG. 1 with a portionthereof shown in section along section line 2-2 in FIG. 1.

FIG. 3 is a sectional view of the apparatus of FIG. 2 along the sectionline 3-3 of FIG. 2.

FIGS. 4 and 5 are fragmentary sectional views illustrating one aspect ofthe removal of the molded plastic structure from the mold.

Where used in the various figures of the drawings, the same numeralsdesignate the same or similar parts. Furthermore, when the terms right,left," top," and bottom are used herein, it should be understood thatthese terms have reference only to the structure shown in the drawingsas it would appear to a person viewing the drawings and are utilizedonly to facilitate describing the invention.

DESCRIPTION In the figures, rotatable molding apparatus generallydesignated as 10 is shown. Molding apparatus 10 includes a hollow mold12 having top and bottom semi-spherical halves l4 and 16, respectively,which are joined together by annular flanges 18 and 20. Flange 18 isjoined with the semi-spherical mold top 14 around the circumference ofmold top 14, and lies in a plane of the major diameter of semi-sphericalmold top 14 extending outwardly from the center of mold top Flange 20 issimilarly joined to mold bottom 16. The halves of.

mold 12 may be assembled to present a spherical inside molding surface22 to plastic material which inside surface encloses an internal chamber23. The halves of mold 12 are assembled by a plurality of bolts 24passing downward through holes formed around and through flange 18 andthrough underlying aligned holes formed around and through flange 20 andby a plurality of nuts 26 secured to bolts 24 above flange l8 andbeneath flange 20. Bolts 24 also fix mold 12 to a horizontally arrangedplatform 28. In particular, bolts 24 have threads formed on their lowerends 30 which threaded ends are received within suitably threadedapertures formed within platform 28. Bolts 24 and platform 28 aretogether termed a cage in the rotational molding art because of theirappearance.

The rotational movement of mold I2 is provided through platform 28. Inparticular, a first bevel gear 32 is integrally formed with a bottom endof a vertically arranged cylinder 34 functioning as a shaft. The top endof cylinder 34 passes through a central aperture 36 formed in platform28, and cylinder 34 is attached to platform 28 by welding. Cylinder 34and gear 32 are journalled upon a further vertically arranged cylinder38 which has an outer diameter less than the inner diameter of cylinder34 to admit bearing material 40 between cylinders 34 and 38.

The ends of cylinder 38 extend above and below the ends of cylinder 34,and retaining rings 42 and 44 are fitted within slots formed around thecircumference of cylinder 38 immediately above and below the ends ofcylinder 34 to provide stops and prevent vertical movement of cylinder34 with respect to cylinder 38.

Cylinder 38 has threads formed on a bottom end 46, and end 46 isarranged to be received within a suitably threaded bore 48 formed in acentral enlarge portion 50 of a horizontally arranged driveshaft 52.Shaft 52 has a left end 54 journalled in a bearing 56 positioned withina suitable support 58 and has a right end 60 journalled within a bearing62 positioned within a suitable support 64.

A pulley 66 is fixed to shaft 52 by a pin 68 to cause pulley 66 torotate with shaft 52. A belt 70 is arranged within pulley 66 and isfurther arranged to be driven by conventional drive means not shown soas to rotate pulley 66 and hence shaft 52 about a horizontal axisparallel to the plane of FIGS. 1 and 2 and at right angles to the planeof FIG. 3. The rotation of shaft 52 causes similar rotation of platform28, bolts 24, and hence mold 12 since cylinder 38 which is fixed to theenlarged portion 50 of shaft 52 supports cylinder 34 which is fixed toplatform 28.

Mold 12 is also rotatable about a vertical axis which axis is at rightangles to the plane of FIG. 1 and parallel to the plane of FIGS. 2 and3. In particular, a second pulley 72 is fixed to the right end of acylinder 74 by a pin 76. Cylinder 74 is positioned around shaft 52 withthe inner diameter of cylinder 74 greater than the outer diameter ofshaft 52 such that bearing material 78 is received between cylinder 74and shaft 52. A second bevel gear 80 is integrally formed upon the leftend of cylinder 74 to engage bevel gear 32. That is, bevel gear 32 isarranged in a horizontal plane on cylinder 34 and bevel gear 80 isarranged in a vertical plane on cylinder 74 such that gears 32 and 80are in meshing relationship. A belt 82 is arranged to be moved byconventional, means not shown, and to rotate pulley 72 around ahorizontal axis. The rotation of pulley 72 causes the rotation ofcylinder 74 and hence bevel gear 80 about a horizontal axis. Therotation ofgear 80 rotates gear 32 and hence cylinder 34 and platform 28around a vertical axis to thus rotate mold 12 about a vertical axis.

Shaft 52 further includes a bore 84 formed along its centrallongitudinal axis. The right end of bore 84 communicates with a hose 86arranged to be connected to a source of fluid pressure. The left end ofbore 84 communicates with a further vertically arranged cylinder 88.Cylinder 88 extends upward through enlarged portion 50 of shaft 52,within and beyond the top of vertically arranged cylinder 38. The topend of cylinder 88 is arranged to receive a downward extending neckportion 90 of lower portion 16 of mold 12. Neck portion 90 fits withinthe inner diameter of cylinder 88 and is fixed to cylinder 88 by aplurality of removable bolts 92, two of which are best shown in FIG. 3.The lower end of cylinder 88 is closed by an integrally formed end 94.

The inside of cylinder 88 forms an air cylinder 96 with cylinder 96communicating with bore 84 of shaft 52. An air piston 98 is positionedwithin cylinder 96 for vertical reciprocal motion with respect tocylinder 88. The lower face of piston 98 and end wall 94 form apneumatic chamber 100 with cylinder 96 which chamber receives the fluidpressure existing in bore 84 to control the movement of piston 98.Piston 98 is urged downward by a spring 102 having one end contactingneck 90 of mold 12 and the other end contacting the upper face of airpiston 98. Spring 102 urges piston 98 downward until piston 98 isstopped by projecting stops 101 positioned in cylinder 88. Stops 103 arein the form of a retaining ring further used to maintain the position ofcylinder 88 with respect to enlarged portion 50 of shaft 52. Anadditional retaining ring 103 is shown positioned in the outside ofcylinder 88 below portion 50 of shaft 52 to further maintain theposition ofcylinder 88.

A container 104 formed of an insulating material such as a hightemperature teflon is positioned substantially centrally of the interior23 of mold 12. In particular, container 104 is formed of verticallyarranged cylindrical side walls 106 and a horizontally arranged bottomend wall 108 integrally formed with side walls 106. A vertically andaxially arranged disc-like cover 110 is arranged to coact with insulatedcontainer 104 in a first position for sealing the end of the insulatedcontainer 104 to prevent the contents of insulated container 104 fromentering internal chamber 23 of mold 12. As shown, cover 110 is in asecond or open position for allowing the contents of insulated container104 to enter the interior chamber 23 of mold 12 at a preselected timewith respect to the molding process, as will be explained.

The control of cover 110 is through the movement of piston 108 which isconnected to cover 110 through a vertically arranged shaft 112, also ofa thermally insulating material such as phenolic, connected to the lowerface of cover 110 and a vertically arranged shaft 114 attached to theupper face of air piston 98. Shafts 112 and 114 are interconnected by anoverfitting, removable, cylindrical, detent fastener 116. A movement ofcover 110 from a first to a second position is thus caused by themovement of piston 98 from a first or closed to a second or openposition within cylinder 98.

Shafts 112 and 114 move within a vertically arranged cylinder 118mounted concentrically within and fixed to insulated container 104 aboutshaft 112. Cylinder 118 further passes downward through neck of bottomhalf 16 of mold 12 to allow shaft 112 to exit from mold 12. Shaft 114meets shaft 112 within the coils of spring 102, and detent 116reciprocally moves within spring 102.

In FIG. 3, a first plastic material 120 is shown as molded to the insidesurface 22 of mold 12 to form an outer layer of a hollow laminatedstructure and a second plastic material 122 is shown within insulatedcontainer 104.

OPERATION In molding an article according to the preferred embodiment ofthe present invention, assume the rotation of the mold is stopped suchthat mold 12 is in a vertical position as is shown in the figures. Thefirst plastic material 120, in the form of a powdered polyethyleneplastic, is added to internal chamber 23 of mold 12. Fluid pressure isapplied through hose 86, through bore 84, to pneumatic chamber 100, andthus to the lower face of piston 98. Piston 98 moves from its firstposition adjacent stop 101, against the action of spring 102, and to asecond position determined by the level of air pressure applied.

Up to this point, the action of spring 102 has maintained cover in afirst position to coact with insulated container 104 and seal insulatedcontainer 104 to prevent the contents of that container from enteringthe interior chamber 23 of the mold. Upon the application of fluidpressure to piston 98, the piston and hence cover 110 moves with respectto container 104 from its first to its second or open position to thusallow access to the interior of insulated container 104. A secondplastic material 122 such as powdered nylon is then added to theinterior of insulated container 104, fluid pressure is removed, andcover 110 again coacts with insulated container 104 to seal it.

The mold is then sealed, placed in an oven (not shown) or otherwiseheated, and rotated. Rotational drive means without the oven (not shown)are actuated to move belts 70 and 82 which belts in turn rotate pulleys66 and 72 which are also maintained without oven unless heat resistantbelts such as chain drives are used. The rotation of pulleys 66 and 72rotate mold 12 about a vertical and about a horizontal axis to providebiaxial molding of plastic within the spherical mold. The rota tionalspeed maintained is very slow, less than 20 revolutions per minute, suchthat the force upon the powdered polyethylene material is gravitationalin nature and not centrifugal.

After a time, the heated mold transmits sufficient heat to the powderedpolyethylene material to change it from a powdered state to a liquidstate whereby the polyethylene material coats the inside surface 22 ofmold 12, as is shown in FIG. 3. While the polyethylene is in this fusedstate, fluid pressure is applied to piston 98 to release the powderednylon 122 from the interior of insulated container 104, as described.

Since the polyethylene is in a fused state, the heat stored within thepolyethylene rapidly brings the powdered nylon to a fused state also.Thus, a layer of nylon is deposited over the inside surface of thepolyethylene 120, and the nylon is rapidly brought to a fused statealso.

It is to be noticed that the rotation and heating of the mold was notinterrupted since the nylon was previously deposited in the insulatedcontainer 104. Note should also be made that the addition of the nylonto the interior 23 of mold 12 can be lOlO29 (Q0 accomplishedautomatically after the process times have been determined by a simpletimed control of the fluid pressure provided to hose 86. If not desired,the addition of the nylon from insulated container 104 may also beinitiated manually by manually controlling the fluid pressure providedto hose 86.

After the nylon has reached a fused state and is properly molded, themold is spray cooled with water to set the condition of the plasticwhile the mold is moved, the mold 12 is removed from the oven, and themold 12 is fast cooled with a volume of water. At this point, thepolyethylene and the nylon form an integral hollow laminated plasticstructure at least since they have cooled through their melting pointstogether.

To remove the molded article, nuts 26 are removed from bolts 24, and thetop 14 of mold 12 is removed. Also, bolts 92 holding neck 90 of thebottom portion 16 of mold 12 to cylinder 88 are removed and the bottomone half 16 of mold 12 including the molded article can be removed fromthe rotational apparatus by removing shaft 112 and detent fastener 116from shaft 114, as shown in FIG. 4. A plug of laminated plastic material124 is then cut from the molded article, as shown in FIG. 5, andinsulated container 104 is removed.

While the method and apparatus of the present invention apply for manycombinations of similar and dissimilar materials, one valuableembodiment is a polyethylene outer layer and a nylon inner layer. A highdensity polyethylene (specific gravities of from 0.95 to 0.96) such asDupont Alathon (trademark) types 7040 or 7140 or the high densitypolyethylene produced by Fusion Rubbermaid may be used for the.firstplastic material 120. Also, a medium density (specific gravity around0.93) polyethylene such as microthene 715 or 711 produced by the UnitedStates Industrial Chemical Company may be used. Nylon 12 such as typesLl600 and Ll6l0 produced by Allied Chemical Company can be used for thenylon inner layer with good results. Also, types Ll940 and N190] alsoproduced by Allied Chemical Company may be used. Nylon 6 produced by theJ. P. Money Company or Micropel 6000 produced by Nypel Company may beused.

Using the above materials, the first and second plastic materials areplaced in their respective positions in the mold in powdered form of 35mesh. The mold is placed in the oven which oven is maintained at atemperature ranging between 525 and 640 Fahrenheit. During the time inthe oven, the mold is rotated at a low speed of between six to 15revolutions per minute. In order to properly mold the polyethylene andrender it in a fused state, 11 to 17 minutes are needed of heating androtation. A layer of polyethylene on the order of 80 to I00 mils may beformed during this time. Fluid pressure is applied to piston 98 torelease the powdered nylon after the eleven to seventeen minute intervaland an additional molding and heating time of l to 7% minutes isrequired for thenylon to reach a fused molded state. A thin layer of 30mils of, nylon may be deposited in one minute while a relatively thicklayer of 135 mils of nylon may be deposited in seven and a half minutes.

Thus, an integral laminated molded article formed from at least twoplastic materials may be formed using the teachings of the presentinvention.

Now that the teachings of the present invention have been explained,many extensions and variations will be obvious to one skilled in theart. For example, while the preferred embodiment of the presentinvention has been explained with respect to specific materials, times,temperatures, thicknesses, and configurations, no restriction to thesespecified items is intended.

Further, the exact rotational speed of the mold will depend upon thesize and configuration of the article to be molded. If the article to bemolded does not have symmetry about all axes of rotation, such as thesphere illustrated, the rotational speed about the individual axesshould be adjusted to control the speed of the flow of plastic materialsacross the mold surface to be equal about all axes.

Additionally, the preferred embodiment has been explained with respectto material in the powdered form using a biaxial molding process. Nolimitation to the powdered form or a two axis molding system isintended. One axis or three axes may be used, and material in liquid orpowder form will function with the apparatus and method of the presentinvention.

Further, it is not necessary that insulated container 104 be inside ofmold 12. The interior chamber 23 of mold 12 is the most appropriate andpreferred position since it is desired to shield the second plasticmaterial 122 contained within insulated container 104 from the heat toavoid fusion until the proper moment for its release and since theinterior of mold 12 is the last place associated with mold 12 to beheated, i.e., it is the most shielded position. Insulated container 104may be placed on the outside of mold 12 with proper provision for theentrance of the material 122 into the mold and with proper heatshielding.

Furthermore, while the configuration of insulated container 104 wasshown as cylindrical, no limitation to this particular configuration isintended.

Still furthermore, the opening allowing the entrance of material fromthe insulated container may be in the side of the container rather thanin the top. An example of this is where the insulated containercomprises an inner and an outer container which may be rotated withrespect to one another to align holes formed in both of them. In thiscase, the cover is the outer cylinder which prevents the material withinthe inner container from entering the interior of the mold in somecircular orientations of the inner and outer cylinders, and allows thematerial within the inner container to enter the interior of the mold inother circular orientations.

Likewise, the means for moving the cover with respect to the insulatedcontainer may be an electrical solenoid, hydraulic means or other meansrather than the fluid piston arrangement shown.

Similarly, in molding some articles, it may not be necessary to furtherheat the mold after the second plastic material 122 is released withinthe internal chamber 23. The heat stored in the first plastic materialin a fused state may be adequate to bring the second plastic material122 to a fused state and properly mold it. This depends strongly on thethickness of the layer of the second plastic material 122 desired to bemolded and integrally adhered to the inside surface of the first plasticmaterial 120.

Thus since the invention disclosed herein may be embodied in otherspecific forms without departing from the spirit or generalcharacteristics thereof, some of which forms have been indicated, theembodiments described herein are to be considered in all respectsillustrative and not restrictive. The scope of the invention isindicated by the appended claims, rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are intended to be embraced therein.

What is claimed is:

l. In conjunction with apparatus for performing rotational molding byrotating and heating a plastic material around at least one axis ofrotation, the apparatus including a mold, means for rotating the moldabout the one axis, and means for heating the mold, improved apparatusfor molding laminated hollow structures from plastic material,comprising in combination:

a. insulated container means having a portion thereof open to theinterior of the mold;

b. cover means arranged to coact with the open portion of the insulatedcontainer means for sealing the insulated container means and preventingthe contents of the insulated container means from entering the interiorof the mold; and

c. controlled actuating means connected to the cover means for movingthe cover means with respect to the insulated container means forallowing the contents of the insulated container means to enter theinterior of the mold at a preselected time with respect to the moldingprocess, comprising:

mm'ro nAnA aa. cylinder means adapted to be connected to a source offluid under pressure;

bb. piston means connected to the cover means, the

cc. means for normally maintaining the piston means in the firstposition; and

dd. means for controlling a supply of fluid under pressure to thecylinder means, the introduction of the fluid under pressure overcomingthe effect of means (cc) and causing the piston means to assume thesecond position to allow the entrance of material within the insulatedcontainer means into the interior of the mold.

2. The apparatus of claim 1, wherein means (cc) for normally maintainingthe piston means in the first position comprises a spring.

3. The apparatus of claim 1, wherein:

aa. the insulated container means includes a connection passing throughthe mold and attaching to at least one of the means for rotating themold, the connection being hollow and extending through the insulatedcontainer means;

bb. the cover means comprises a removable end of the insulated containermeans; and

cc. a shaft interconnects the removable end of the insulating containermeans with the piston, the shaft passing through the hollow portion ofthe insulating container means and the hollow portion of the connectionmeans so as to avoid contact with the material within the insulatingcontainer means.

4. The apparatus of claim 3, wherein:

aa. the means for rotating the mold simultaneously rotates the mold ontwo axes substantially rotated from each other; and

bb. the mold is symmetrical about each of the axes or rotation.

1. In conjunction with apparatus for performing rotational molding byrotating and heating a plastic material around at least one axis ofrotation, the apparatus including a mold, means for rotating the moldabout the one axis, and means for heating the mold, improved apparatusfor molding laminated hollow structures from plastic material,comprising in combination: a. insulated container means having a portionthereof open to the interior of the mold; b. cover means arranged tocoact with the open portion of the insulated container means for sealingthe insulated container means and preventing the contents of theinsulated container means from entering the interior of the mold; and c.controlled actuating means connected to the cover means for moving thecover means with respect to the insulated container means for allowingthe contents of the insulated container means to enter the interior ofthe mold at a preselected time with respect to the molding process,comprising: aa. cylinder means adapted to be connected to a source offluid under pressure; bb. piston means connected to the cover means, thepiston means arranged to be reciprocably movable within the cylindermeans so as to assume a first position for causing the cover means toseal the insulated container means and prevent material within theinsulated container means from entering the interior of the mold and toassume a second position for causing the cover means to be movedrelative to the insulated container means for allowing material withinthe insulated container means to enter the interior of the mold; cc.means for normally maintaining the piston means in the first position;and dd. means for controlling a supply of fluid under pressure to thecylinder means, the introduction of the fluid under pressure overcomingthe effect of means (cc) and causing the piston means to assume thesecond position to allow the entrance of material within the insulatedcontainer means into the interior of the mold.
 2. The apparatus of claim1, wherein means (cc) for normally maintaining the piston means in thefirst position comprises a spring.
 3. The apparatus of claim 1, wherein:aa. the insulated container means includes a connection passing throughthe mold and attaching to at least one of the means for rotating themold, the connection being hollow and extending through the insulatedcontainer means; bb. the cover means comprises a removable end of theinsulated container means; and cc. a shaft interconnects the removableend of the insulating container means with the piston, the shaft passingthrough the hollow portion of the insulating container means and thehollow portion of the connection means so as to avoid contact with thematerial within the insulating container means.
 4. The apparatus ofclaim 3, wherein: aa. the means for roTating the mold simultaneouslyrotates the mold on two axes substantially 90* rotated from each other;and bb. the mold is symmetrical about each of the axes or rotation.